1
: a splitting or breaking up into parts
2
: reproduction by spontaneous division of the body into two or more parts each of which grows into a complete organism
3
: the splitting of an atomic nucleus resulting in the release of large amounts of energy
fissioned; fissioning; fissions
: to undergo fission
: to cause to undergo fission
Examples of fission in a Sentence
Recent Examples on the Web
New Atlas, 15 Apr. 2025
Join 16 others in the comments View Comments Some experts believe the Mianyang site may end being a different kind of fusion facility, a hybrid of fusion and fission.
—Laura Paddison, CNN, 5 Feb. 2025
Washington Post, 28 Apr. 2022
The point is that by analyzing the array of radioactive fission products – those that can be captured and analyzed – nuclear forensic specialists can start to figure out if the atoms that fissioned were U-235, Pu-239, or (in some cases) U-238.
—Andrew Karam, Popular Mechanics, 7 Jan. 2016
See All Example Sentences for fission
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Noun
This produces greater uranium density, improves thermal conductivity, and reduces gas released by the fission process that can damage fuel.
—New Atlas, 15 Apr. 2025
Join 16 others in the comments View Comments Some experts believe the Mianyang site may end being a different kind of fusion facility, a hybrid of fusion and fission.
—Laura Paddison, CNN, 5 Feb. 2025
Verb
Most atoms do not fission, but the isotopes of certain elements, such as uranium-235, are fissile.
—Washington Post, 28 Apr. 2022
The point is that by analyzing the array of radioactive fission products – those that can be captured and analyzed – nuclear forensic specialists can start to figure out if the atoms that fissioned were U-235, Pu-239, or (in some cases) U-238.
—Andrew Karam, Popular Mechanics, 7 Jan. 2016
See All Example Sentences for fission
Cite this Entry
“Fission.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/fission. Accessed 4 May. 2025.
Copy CitationKids Definition
fission
1 of 2 noun
fis·sion
ˈfish-ən 
also ˈfizh-
1
: a splitting or breaking up into parts
2
: a method of reproduction in which a living cell or body divides into two or more parts each of which grows into a whole new individual
3
: the splitting of an atomic nucleus resulting in the release of large amounts of energy
fission
2 of 2 verb
fissioned; fissioning
ˈfish-(ə-)niŋ,
ˈfizh-
: to go through or cause to go through fission
Medical Definition
fission
noun
fis·sion
ˈfish-ən also ˈfizh-
1
: a method of reproduction in which a living cell or body divides into two or more parts each of which grows into a whole new individual
2
a
b
: the splitting of an atomic nucleus resulting in the release of large amounts of energy
called also nuclear fission
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